mail-to-commit-mapping: notify the user before fetching refs

Fetching refs in a new repository is potentially expensive; Let's let
the user know what is happening in that case.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

lib/mail-commit-mapping.ts

@@ -42,6 +42,7 @@ export class MailCommitMapping {
             refs.push(`+refs/heads/*:refs/remotes/${this.config.repo.maintainerBranch}/*`);
         }
         if (refs.length) {
+            console.log(`Updating mail-to-commit/refs: ${refs.join(", ")}`);
             await git(["fetch", `https://github.com/${this.config.repo.owner}/${this.config.repo.name}`, ...refs], {
                 workDir: this.workDir,
             });